Photoelectric switch means



March 27, 1962 K. F FRANK PHOTOELECTRIC SWITCH MEANS Filed July 20, 1959 2 Sheets-Sheet -1 m OE - air.

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INVENTOR. KARL F. FRANK March 27, 1962 K. F. FRANK 13,

PHOTOELECTRIC SWITCH MEANS Filed July 20, 1959 2 Sheets-Sheet 2 FIGS FIG 5A FIG 5B INVENTOR KARL F. FR ANK BY fwfww United States Patent Ofifice 3,027,495 Patented Mar. 27, 1962 3,027,495 PHOTOELECTRIC SWlTCH MEANS Karl F. Frank, Garden City, N.Y., assignor to Micro Balancing, Incorporated, Garden City Park, N.Y., a corporation of Delaware Filed July 20, 1959, Ser. No. 828,359 3 Claims. (Cl. 317-124) This invention relates to automatic control means and more particularly to automatic control of lights.

This application is a continuation-in-part of my prior application Serial No. 723,405, filed March 24, 1958, for Light Sensitive Control Means, now Patent No. 2,900,520.

It is desirable to have individual automatic control for street and other lights for several reasons. *It is preferable to decentralize control as much as possible in order to isolate trouble so that one failure would not disrupt more than one light. It is too expensive and not practical to lay separate control cables. Therefore, it is the usual practice to put individual switches in each light.

Some prior automatic devices for turning street lights on and off generally include an electric clock. These systems are expensive and must be individually reset as ,the days become longer and shorter. Other devices have included photocells operating magnetic relay and vacuum tube circuits. One difficulty with these systems is that they areresponsive to intermittent light such as lightning and passing automobile lights. Also magnetic relays and vacuum tubes are sources of continual trouble, and in street lighting, maintenance is an important item. Radio controlled systems are unduly complicated and are subject to interference such as automobile ignition and atmospherics.

Therefore, there is a need for automatic lighting control means which is fully automatic, which does not require resetting as the days lengthen and shorten, which is-not responsive to intermittent light such as lightning or automobile headlights, or to other types of interferences, and which eliminates all magnetic relays and Vacuum tubes.

The present invention provides such automatic street lighting control. It comprises generally a photocell, temperature compensated snap action contact means responsive to the average output of the photocell, and adjustment means for said contact means. All vacuum tube amplifiers and magnetic relays are eliminated.

Accordingly, a principal object of the invention is to provide new and improved automatic lighting control means.

A further object is to provide thermostatic means where the contact separation is insensitive to ambient temperature.

Still another object is to provide new and improved thermal control means.

A still further object of the invention is to provide control means having a useful thermal output.

Another object of the invention is to provide light sensitive automatic control means which are inexpensive and easy to maintain, and which do not use vacuum tubes or magnetic relays.

Another object of the invention is to provide automatic photocell control means connected to directly operate snap action control contacts.

Another object of the invention is to provide a photoelectric switch, a pair of bi-metal strips mounted on insulating block means, a heating coil on one of said himetal strips, said heating coil being connected with said photocell, said bi-rnetal strips being connected to directly operate snap action switch contact means.

- These and other objects of the invention will become apparent from the following specification and drawings, of which: 7

FIGURE 1 is a front view of an embodiment of the invention.

FIGURE 2 is a side view of an embodiment of FIG- URE 1.

FIGURE 3 is a back view of the embodiment of FIG- URE 1.

FIGURE 4 is a circuit diagram FIGURE 1, and

FIGURES 5, 5A, and 5B are detail views of the snap action switch blade assembly.

This invention is an improvement over my above mentioned prior invention. In that invention there were two sets of temperature compensated contacts, one of which carried the control current through the photocell and the other of which carried the load circuit. The present invention eliminates one set of contacts. It has been found that by adding certain adjustment features the contacts may be adjusted close enough together when open and thereby made sensitive enough to be operated by a very low control power.

Referring generally to the figures, the invention generally comprises a pair of bi-metal strips 1 and 2, each mounted at one end to the insulating block means 3. The bi-metal strip 2 is curved sharply at its free end at the point 2' as will be discussed. Snap action contact means 4 operates the contact 5 which is adapted to complete a circuit through the stationary contact 6, also mounted in the insulating block means. Adjustment means 7 are provided for controlling the open spacing of the contacts 5 and 6 independently of any bending of the bi-metal strip 2. A heating coil 8 is mounted on the bimetal strip 1 and is directly connected to the photocell It FIGURE 4, which may be conventional.

The bi-metal strips 1 and 2 are arranged to bend in the same direction in order to compensate for ambient temperature conditions. However, when the photocell is energized the heating coil causes a further differential movement of the bi-metal strip 1 which actuates the snap action switch 4 to close the contacts 5 and 6.

More specifically, the entire assembly is mounted on a panel 11 which may be of plastic. A right angle bracket 12 is riveted or otherwise connected to the panel 11. The right angle bracket 6 is also riveted or otherwise connected to the mounting panel 11. The entire assembly is mounted thereon, by means of screws 13 and 14 and nuts 15 and 16 and the insulating block means.

The bi-metal strip 1 is a flat member with a pair of mounting holes. It is insulated from the bracket 6' by means of the insulating block 3a which may be a ceramic or other insulating block having good electrical and thermal characteristics. The block 3a has two holes to accommodate the screws 13 and 14. The bracket 6' is insulated from the flipper blade back-up strip 17 by means of the insulating block 3b. The flipper blade back-up strip 17 has a U-shaped configuration at its lower end which runs around the lower end of the bi-metal strip 2. The adjustment bracket 12 is an extension of bracket 12. The screw 7 in the bracket 12 extends through apertures in the bi-metal strip 2 and the flipper blade back-up strip 17 for the purpose of adjusting the open spacing of the contact 5.

The contact 5 is mounted on a bi-stable spring element 4a which is spot welded to a raised portion or dimple 35 in the flipper blade back-up strip 17, see also FIGURES 5, 5A, and 5B. The bi-stable spring may be of the type having a center strip formed by two parallel interior slots, the center strip being stretched so as to have bistable or snap action characteristics, as discussed in connection with FIGURE 5. A typical snap action device of the embodiment of 4a is preferably of beryllium copper.

is shown in my copending application, Serial No. 788,430, for Snap Action Switch Means, filed January 22, 1959. Adjustable actuating screw 20 is mounted on the free end of thebi-stable strip 1 and is in contact with the snap action spring 4a, so that upon the applicationof controlled heat .by the heating coil 8, the bi-metal strip 1 will bend towards the birmetal strip 2 causing the snap action spring 4a to snap .to open contactposition shown by the dotted lines in FIGURE 5B, thereby opening the normally closed contacts 5 and 6. The movement of the contact 5 may be adjusted by the adjustment screw 7 so that the movement of the contact 5 need only be about .005 inch or less. The slotted flipper blade contact spring The contacts 5 and 6 may be conventional electrical button-type contacts.

The flipper blade back-up strip 17 is clamped to the second bi-metal strip 2 at its lower end andits upper end bears against the curved end 2 of the bi-metal strip 2 by spring action. The purpose of the curved end of the bi-metal strip 2, is to assure mechanical contact with the flipper blade back-up strip at its end under any ambient temperature, since heating of the bi-metal strip will curve the same, and contact to the flipper blade end with a straight strip can not be accomplished when the bi-metal strip curves away from it.

The adjustment means 7 limits the amount of opening ofthe contacts 5 and 6. If the adjustment means was not provided, extreme temperature variations causing the bimetal; strip 2 to bend would vary the open contact spacing considerably. With the present arrangement, however, the spacing between the stationary contact bracket 6 and adjustment bracket 12' is a constant. This adjustment means controls the open spacing of the contacts so that a very low control power on the order of A2 watt will provide suflicient force tooperate the contacts over a temperature range from 40 to 150 F. 'With the snap action switch of the present invention, currents of amperes may be broken with an open contact spacing on the; order of .005, inch.

d FIGURES 5 and 5A show detail views of the snap action switch blade assembly. The flipper blade back-up strip 17 has a pair of mounting holes and 31 and turned over edges 33. The bottom of the flipper blade r back-up strip 17 is turned over in a U-shape which fits around the bottom of the bi-metal strip 2. An aperture 34 is provided behind the contact 5 .so that the contact may be adjusted by the adjusting screw 7. The flipper blade back-up strip 17 also has a dimple indentation 35 upon which the slotted blade 4a is mounted at one point, for instance, by spot Welding.

The contact snap action blade 4a has two slots 36 and 37 forming a central portionipfl which is deformed or kinlied along the line 39 so that the central portion 38 is longer than the side portions and becomes a bi-stable element which snaps quickly from one position to the other, The blade 41a is preferably made of beryllium copper spring material and the contact 5 is of convenwhich eliminates all magnetic relays and vacuum tubes. 1

The adjustment means of the present invention permit the low power available from a photocell to directly operate contacts in the load circuit. Prior automatic lighting controls have generally included magnetic relays which are subject to chattering and which require a considerable amount of power. Y My prior above mentioned invention eliminated the magnetic relays and vacuum tubes but remetal plates 23, 24, having good heat conducting qualities, form a heat sink underneath the photocell block or plate 10 for the purposes of carrying undesirable heat away from the photocell.

Referring to the figures and the circuit diagram of FIGURE 4, the photocell 10 is connected through spring 22 and rivet 22 to one terminal A whichis connected to. one side of the line L The other end of the photocell is connected through the spring 21 andrivet' 21"and lead 25 to the heating coil 8. The other 'end of the heating coil is connected to the; bi-metal strip 1 d t e e through the mounting screws 13 and 14 to the other side of the line L which is connected to a terminal B on the mounting bracket 12. The stationary contact 6 is con nected to a terminal C.

The movable contact 5 is mounted on the slotted spring flipper blade 4a and electrically connected through the flipper blade back-up strip 17 which is wrapped around the lower end of the second bi-metal strip 2. The current through the contact 5 will not tend to go through the bi-metal strip 2 as a much lower resistance circuit is provided by the U-shaped portion of the flipper blade back-up strip 17 to the right angle bracket 12 and thence to the other side of the line L The load circuit is completed from one side of the line L through the terminal B, bracket 12, flipper blade back-up strip 17, snap action flipper blade 4a, contacts 5 and 6, to terminal C which is connected to the load Z. The other end of the load Z may be permanently connected to L by means of the lead 29.

quired two sets of temperature compensating contacts. The present invention only requires one set of temperature compensating contacts due to the adjustment features and permits operation over a wide range of temperatures.

, Various modifications may be made without departing from the scope of the invention which is defined by the following claims.

I claim:

1. A photoelectric switch comprising a photocell, insulating mounting block means, a first bi-metal 'sttip mounted at one end to said insulating mounting block means, a second bi-metal strip mounted at one end to 7 said insulating mounting block means, said second bidirectly connected to said photocell, a snap action switch contact spring means mounted on said insulating block means including a straight strip member bearing at its free end against said curved free end of said second bi-metal strip, a stationary contact mounted on said insulating block means, and adjustable means mounted at the free end of said first bi-metal strip and adapted to move said snap action spring and contact to meet said stationary contact when said first bi-metal strip is bent by control heat;

2; A photoelectric switch comprising a photocell, insulating mounting block means, a first bi-metal strip mounted at one end to said insulating mounting block means, a second bi-metal strip mounted at one end to said insulating mounting block means, said second bimetal strip being mounted parallel to and curved toward said first bi-metal strip at its free end, a heating coil on said first bi-metal strip, said heating coil being directly connected to said photocell, a snap action switch contact spring mounted on said insulating block means and bearing at its free end against said curved free end of said second bi-metal strip, a stationary contact mounted on said insulating block means, adjustable means mounted at the free end of said first bi-metal strip and adapted to move said snap action spring and contact to meet said stationary contact when said first bi-metal strip is bent by control heat, and means mounted on said second bi-metal strip to control the open spacing of said contacts independently of the bending of said second bi-metal strip.

3. A photoelectric switch comprising a photocell, insulating mounting block means, a first bi-metal strip mounted at one end to said insulating mounting block means, a second bi-metal strip mounted at one end to said insulating mounting block means, said second bimetal strip being mounted generally parallel to said first bi-metal strip and curved toward said first bi-rnetal strip at its free end, a heating coil on said first bi-metal strip, said heating coil being directly connected to said photocell, a snap action switch contact spring means mounted on said insulating block means and including a straight strip member bearing at its free end against said free end of said second bi-metal strip, a stationary contact mounted on said insulating block means, and adjustable means mounted at the free end of said first bi-metal strip and adapted to move said snap action spring and contact to meet said stationary contact when said first bi-metal strip is bent by control heat.

References Cited in the tile of this patent UNITED STATES PATENTS Re. 24,268 Zuckerman Jan. 29, 1957 1,618,816 Davies Feb. 22, 1927 2,054,380 Lamb Sept. 15, 1936 2,057,384 Lamb Oct. 13, 1936 2,796,553 Ronning June 18, 1957 

